With good features not found in natural leather, sheet-like articles consisting mainly of ultrafine fibers and polymer elastic material have been used in various products such as clothing, chair upholstery, and automobile interior material, and they are currently acquiring new applications such as industrial materials as well as outer covering and cases of mobile devices, resulting in demands increasing year after year. Under such circumstances, thinner sheets are now called for to meet diversifying needs and demands are also increasing for high-strength products that meet practical uses. Various proposals have been made aiming to meet these requirements.
Specifically, a study has proposed a method in which a sheet-like article that can serve as industrial material with high strength and pilling resistance can be produced from a suede-like leather sheet composed mainly of ultrafine fibers and an elastic polymer in which the elastic polymer is localized near the surfaces in the thickness direction of nonwoven fabric (see Patent document 1). This proposal is intended to achieve high strength and pilling resistance of the surface by localizing an elastic polymer near the surface region, but as a result of the elastic polymer being localized near the surface region, the fibers are held strongly by the elastic polymer, easily leading to problems such as insufficient napping, short raised fibers, and unsmooth surface quality with rough feel. In this proposal, furthermore, the amount of squeezed liquid resulting from impregnation with a solution or aqueous dispersion of an elastic polymer is adjusted properly and the movement of the elastic polymer toward the surface is controlled during coagulation and during drying in order to localize the elastic polymer near the surface region. In the case of a thin sheet, however, the movement distance is so short in the thickness direction that it will be difficult to perform control as proposed above and accordingly it will be difficult to obtain a high-strength sheet-like article.
Another document proposes an artificial leather produced by inserting high-strength woven fabric into nonwoven fabric that constitutes a sheet-like article, thereby forming a structure in which the quotient of the height of the overlapping portion of the cross section between adjacent yarns in the inserted high-strength woven fabric by the diameter of the yarns of the high-strength woven fabric is 0.25 or less (see Patent document 2). This proposal is intended to increase the strength of artificial leather by inserting high-strength woven fabric, but the proposed woven fabric itself has a significant thickness, making it difficult to provide a thin product.
As stated above, no attempts have ever succeeded in providing a leathery sheet-like article that is thin as well as high in quality and strength.